Ca-sensitive Na transport in sheep omasum
Related Experiment Video
Updated: Oct 20, 2026

Demonstration of Membrane Transport of Histidine using Goat Intestinal Inverted Sacs: An Experiential Pedagogical Tool for Undergraduates
Published on: October 4, 2024
1Department of Physiology, Faculty of Veterinary Medicine, University of Giessen, D-35392 Giessen, Germany.
Abstract:
Na transport across a preparation of sheep omasum was studied. All tissues exhibited a serosa-positive short-circuit current (Isc), with a range of 1-4 microeq. h-1. cm-2. A Michaelis-Menten-type kinetic was found between the Na concentration and the Isc (Michaelis-Menten constant for transport of Na = 6.7 mM; maximal transport capacity of Na = 4.16 microeq. h-1. cm-2). Mucosal amiloride (1 mM), phenamil (1 or 10 microM), or serosal aldosterone (1 microM for 6 h) did not change Isc. Removal of divalent cations (Ca and Mg) enhanced Isc considerably from 2.61 +/- 0.24 to a peak value of 11.18 +/- 1.1 microeq. h-1. cm-2. The peak Isc (overshoot) immediately declined to a plateau Isc of approximately 6-7 microeq. h-1. cm-2. Na flux measurements showed a close correlation between changes in Isc and Na transport. Transepithelial studies demonstrated that K, Cs, Rb, and Li are transported, indicating putative nonselective cation channels, which are inhibited by divalent cations (including Ca, Mg, Sr, Ba) and by (trivalent) La. Intracellular microelectrode recordings from the luminal side clearly showed changes of voltage divider ratio when mucosal divalent cations were removed. The obtained data support the assumption of a distinct electrogenic Na transport mechanism in sheep omasum.
Related Concept Videos
Transcellular Transport of Solutes
Carrier-Mediated Transport
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
The Significance of Membrane Transport
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...
Methods for Studying Drug Absorption: In situ
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...
Osmosis
Water, like other substances, moves from a high concentration of free water...
Osmosis

